Magnetic articles

ABSTRACT

A thin magnetic layer of substantially rectangular hysteretic cycle, specially for use in binary data information magnetic stores, comprised of a ternary alloy of cobalt, tungsten and phosphor. Such a layer is produced on a dielectric or metallic substrate from a chemical autocatalytic process.

United States Patent Blanchard 1 Mar. 7, 1972 [54] MAGNETIC ARTICLES 235, 240

[72] Inventor: Joseph Louis Blanchard, Saint-Joseph, [56} References Cited France [73] Assignee: Compagnie Internationale Poure L'lnfor- UNITED STATES PATENTS q Les C1ayes-s0us-B0is,Frane 3,370,979 2/1968 Schmeckenbecher ..75 170 [22] Filed: 10,1969 3,558,306 1/1971 Mathias et a1. ..75/170 [21] Appl. No.: 805,859 Primary Examiner-Richard 0. Dean Attorney-Kemon, Palmer and Estabrook [30] Foreign Application Priority Data [57] ABSTRACT Mar. 26, France A g i layer of substantiany rectangular hysteretic cycle, specially for use in binary data information magnetic [52] US. Cl ..29/19l, 29/194, 75/170, Stores comprised of a ternary alloy of cobalt, tungsten and 1 17/240 148/3155 340/174 340/174'1 phosphor. Such a layer is produced on a dielectric or metallic [51] Int. Cl ..B32b 15/00 Substrate from a chemical autocatalytic process [58] Field 01' Search.. ...75/l70, 171; 148/32, 31.55,

8 Claims, No Drawings SUMMARY OF THE INVENTION The invention is concerned with the composition and production of thin layers, or films, of magnetic alloys having a substantially rectangular hysteretic cycle coated upon discs, drums, tapes, sheets and the like intended to enter in the constitution of magnetic stores of binary data.

It is more particularly concerned with such layers or films which are produced by depositing their materials from a chemical autp c a talytic reaction onto metallic or dielectric substrates. Such a method is generally known and comprises merging a previously sensibilized substrate within a heated solution of salts of the elements of the layer to produce and of at least one agent for reduction of the metallic ions of said salts, the length of said operation being adjusted to the thickness of the layer which is wanted.

It is an object of the invention to provide new compositions of such magnetic thin layers or films and it is a further object of the invention to provide an improved method for producing such new magnetic films or layers.

It is a further object of the invention to so provide the constitution of such films or layers and their method of production that the resulting products are of high-coercive magnetic field and of high homogeneity of their material, for enabling a high density of the binary information data therein.

It is a further object of the invention to so provide the constitution of such films or layers and their method of production that the reproductibility of the magnetic properties thereof is duly ensured from layer to layer, or film to film, in an industrial production thereof.

According to a feature of the invention, such a magnetic thin layer or film is comprised of a ternary alloy of cobalt, tungsten and phosphor.

According to a further feature of the invention, said alloy comprises, per weight, about 90 to 92 percent of cobalt, about 6 to percent of tungsten and about 0.5 to 3 percent of phosphor; the preferred alloy comprising 91 percent of cobalt, 8 percent of tungsten and 1 percent of phosphor.

According to a further feature of the invention, such a layer or film of said ternary alloy is produced from a catalytic bath made of an aqueous solution having an alcaline pH of about 8.4 to 9 and containing salts of cobalt and tungsten and hydrophosphite of sodium, deposition being produced at a temperature substantially comprises between 75 and 85 C. regulated during the operation at a value not varying more than 1 C.

It is preferred to introduce the tungsten as a sodium tungstate salt; and it is also preferred to introduce in said bath, after solving cobalt sulfate therein, Rochelle salt as a complexant agent.

DETAILED DESCRIPTION The following considers a preferred constitution of a magnetic thin layer or film according to the invention, and from this single example, one may easily deduce any other constitution of such layers or films.

Said preferred constitution comprises, per weights, 9] percent cobalt, 8 percent tungsten and l percent phosphor, which corresponds in metallic atom composition to 95 percent cobalt, 2.3 percent tungsten and 2.2 percent phosphor. Such a layer presents, for a thickness of the order of 5,000 A., a coercive field value substantially equal to 400 OE; the thickness of a layer is, when required, modified at will from a mere adjustment of the length of the deposition operation proper, and the range of thicknesses which are considered as useful for the contemplated application of such layers as integrated parts of binary data magnetic stores, approximately extends from about 3,000 A., wherefor the coercive field is of about 480 OE, up to about 6,000 A., wherefor the coercive field is of about 300 Oersteds. Such a range of values of the coercive field of magnetic material films having a substantially rectangular h steretis cycle or characteristic, is of special interest for use In mary data information stores because, in addition to a fair protection against the effect of stray demagnetizing magnetic fields on the content of the store, they do not request specially drastic performances for the write or read-in heads by means of which the information is entered in the store.

Variations of said constitution within the ranges of about 90 to 92 percent weight of cobalt, 6 to 8 percent weight of tungsten and 0.5 to 3 percent weight of phosphor do not largely vary the above given figures, but the useful range of layer or film thicknesses is restricted from use of such modifications if one wish to maintain the possibility of range of the coercive field values.

For the preferred above-defined constitution, the method of production which has proved the more efficient is as follows, wherein, inter alia, the sequence of operations in preparing the autocatalytic bath has proved to be of great importance for the final result, both from the point of view of the reproducibility and from the point of view of performances of the films.

A substrate which may be indifferently made of dielectric or metallic material is previously sensibilized according to any conventional method in this respect, useless to detail here.

The autocatalytic chemical bath is prepared as follows: it may be noted that one liter of said bath will permit the straight deposition of the film over 15 dm. of substrate, without addition of any extra bath solution during an operation. The under described components are given for such a one liter of bath.

The first step of formation of the bath comprises solving 0.426 Mol of cobalt sulfide Co 80,, 7 H O in hot distillated water which is strongly agitated during this operation. The second step comprises adding a complexing agent, preferably Rochelle (Seignette) salt by 1.45 Mol proportion. Let the solution thicken from the addition of the said complexing agent. The third step comprises the introduction in the solution of 0.94 Mol of NH OH, corresponding to a pH determination at about a value of 8.5. The solution clears. When the lim'pidity is obtained, the fourth step comprises solving therein 0.137 Mol of sodium tungstate Na W0 Now, a solution containing sodium hypophosphite Na H P0 H O is separately prepared, wherein, if estimated useful, 0.94 Mol of NH, Cl is also introduced. Said last solution is mixed with the preceding, by volumes containing at most 5 gr. of solid solved in it up to a content of the first solution by 0.38 Mol of sodium hydrophosphite.

The thus resulting bath is brought to a temperature of C.

and the sensibilized substrate is plunged within said bath. An I autocatalytic reaction develops whereby a layer of the ternary alloy cobalt-tungsten-phosphor is obtained in the above disclosed proportions of its elements. In about 4 minutes, said reaction produces a film having a thickness of the order of 3,000 A. The thickness will reach about 5,000 A. within about 6 minutes and about 6,000 A. within about 8 minutes.

As said, variations of the ratio and proportions of elements in the alloy are plainly obtained by varying the percentages in Mols introduced in the solution, without varying the succession of the above defined steps.

What is claimed is:

l. A magnetic article comprising a substrate coated with a thin magnetic layer of substantially rectangular hysteretic loop from electroless deposition on said substrate of a thin layer of a ternary alloy consisting essentially of about to 92 percent by weight of cobalt, about 6 to 10 percent by weight of tungsten and about 0.5 to 3 percent by weight of phosphor.

2. An article of claim 1 wherein said alloy consists of 91 percent cobalt, 8 percent tungsten and 1 percent phosphor.

3. An article of claim 1 wherein said substrate is a dielectric material.

4. An article of claim 1 wherein said substrate is a metal.

5. An article of claim 1 wherein the substrate is a disc.

6. An article of claim 1 wherein the substrate is a drum.

7. An article of claim 1 wherein the substrate is a tape.

8. An article of claim 1 wherein the substrate is a sheet. 

2. An article of claim 1 wherein said alloy consists of 91 percent cobalt, 8 percent tungsten and 1 percent phosphor.
 3. An article of claim 1 wherein said substrate is a dielectric material.
 4. An article of claim 1 wherein said substrate is a metal.
 5. An article of claim 1 wherein the substrate is a disc.
 6. An article of claim 1 wherein the substrate is a drum.
 7. An article of claim 1 wherein the substrate is a tape.
 8. An article of claim 1 wherein the substrate is a sheet. 